In injection systems, inadmissible pressure increases can occur in the system in the event of a fault. In particular in the case of modern injection systems which have high-pressure pumps controlled by means of a digital inlet valve, problems can arise in an inlet valve of said type. Specifically, in the case of a normally-open inlet valve which is held in the open state by a spring, in the event of a spring fracture, undesired or excessively early closure of the valve during the delivery phase of the high-pressure pump can result in an undesired pressure build-up in the high-pressure region, caused by an undesired delivery rate of or full delivery by the high-pressure pump up to a critical pressure level. Such a fault can lead to an undesired pressure build-up in the high-pressure volume, which can damage the system and possibly lead to external leakage.
To prevent such damage, it is known for a pressure limiting valve (PLV) to be provided in order to protect the system and the components in the high-pressure region, which pressure limiting valve prevents an excessive build-up of pressure. Said pressure limiting valve is generally a mechanical overpressure valve which is connected to the high-pressure-conducting components, for example to the high-pressure pump, to the high-pressure accumulator (rail) or to the injectors, and which discharges excess fuel quantities from the high-pressure system, for example into the pump return line or into a separate return line.
For rail pressure regulation (pressure regulation in the high-pressure accumulator), the single-controller system described above uses only volume flow regulation of the high-pressure pump by means of said inlet valve.